All installations and services must be performed by qualified service personnel.

1.Electrical Branch Supply Circuit

Route all electrical wiring to the left side of the furnace. The power supply circuit to the furnace must be installed and grounded in accordance with the provisions of the National Electrical Code, ANSI/NFPA-70-1999, or latest edition, and all local codes having jurisdiction.

2.Connection Of Power Supply Wires

a.Remove the furnace control panel cover.

b.Insert 120 VAC wires through the strain relief bushing (or conduit connection as applicable) on the left side of the furnace junction box.

c.Connect the “Hot” wire to the terminal block lug marked “L1”.

d.Connect the “Neutral” wire to the terminal block lug marked “L2”.

e.Connect the “ground” wire to the terminal block lug marked “G”.

f.Reinstall and secure the control panel cover with the original mounting screws.

3.Connection Of Thermostat Wires

NOTE: Class 1 thermostat wire must be used inside the furnace burner compartment.

a.Insert 24 VAC wires through the plastic grommet on the left side of the furnace casing.

b.Connect the thermostat wires to the yellow leads from the burner (refer to the applicable wiring diagram).

c.Connect the thermostat wires to the room thermostat.

IMPORTANT: The room thermostat should be installed 4 to 5 feet above the floor on interior wall which is relatively free from direct sources of heat (sunlight or supply airflow) or exposure to cold (drafts from open windows and doors). The nominal anticipator settings are 0.8 amperes, for the GMC, and 0.2 amperes, for the OMC (refer to the thermostat literature for additional information).

Five-conductor thermostat wire is recommended for 24 VAC, low-voltage, control circuit wiring. Only 2 wires are required for the furnace (a heating application only).

Electrical Wire Diameter

(AWG)

24

22

20

18

Maximum Recommended Thermostat Wire Length

(feet)

55

90

140

225

24

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Thermo Products GMC-85, OMC-70 service manual Awg
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GMC-85, OMC-70 specifications

Thermo Products has built a reputation for delivering top-notch heating and cooling solutions, and the GMC-85 and OMC-70 models are no exception. These high-efficiency gas furnaces are designed to meet the diverse needs of homeowners while prioritizing energy savings and comfort.

The GMC-85 model is known for its impressive efficiency ratings, operating at an AFUE (Annual Fuel Utilization Efficiency) of up to 85%. This means that a significant portion of the fuel consumed is converted into usable heat, making it an economically sensible option for heating your home. Additionally, it features a multi-speed blower motor, which allows for better air circulation and consistent heating throughout the living space. This model also includes a durable heat exchanger crafted from high-quality materials, ensuring longevity and reliability in performance.

On the other hand, the OMC-70 furnace offers a slightly lower AFUE rating of 70%, but it shines in certain areas such as cost-effectiveness and straightforward installation. Its reputation for reliability is bolstered by its rugged design and construction that can withstand the rigors of various climates. The OMC-70 also includes a standard efficiency motor, contributing to reduced energy consumption while delivering appropriate heating requirements for smaller spaces.

Both models utilize advanced technology aimed at improving user convenience and efficiency. Features such as electronic ignition systems enhance reliability by eliminating the need for a pilot light, while also providing a quick and efficient startup process. Furthermore, each unit can be easily integrated with smart thermostats, allowing homeowners to manage their heating needs remotely for optimized performance.

Noise reduction is another characteristic that sets these models apart. Both the GMC-85 and OMC-70 employ sound-dampening technologies to ensure quieter operation, providing a peaceful environment for families.

In summary, Thermo Products' GMC-85 and OMC-70 furnaces present excellent options for homeowners looking to achieve comfort and energy efficiency. With their durable construction, advanced technology, and features geared toward enhancing user experience, these models provide reliable heating solutions suitable for various needs and budgets. Investing in either of these products translates to improved energy savings and consistent warmth, making them popular choices in today's competitive market.
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